An eye disease inspection instrument comprising a slit light projection optical system for projecting a slit light along a projecting optical axis to a patient's eye, a first optical system for observing a crystalline lens of the patient's eye at a section which is being illuminated by the slit light, a second optical system including an objective lens having an objective optical axis substantially coaxial with respect to the projecting optical axis for performing an observation under a retroillumination method.